1. Field of the Invention
The present disclosure relates to a method for manufacturing a field-effect transistor.
2. Description of the Related Art
As an example of field-effect transistors, a field-effect transistor utilizing an active layer of an oxide semiconductor is known. The field-effect transistor utilizing the active layer of the oxide semiconductor has a problem that the active layer is exposed to an etching solution, such as an acidic solution, when patterning of a conducting film is performed to form source and drain electrodes.
Generally, the oxide semiconductor used for the active layer is easily dissolved by an etchant (etching solution) used to form the source and drain electrodes. Conventionally, when patterning of the conducting film is performed to form the source and drain electrodes, an etching stopper layer is provided on the oxide semiconductor for preventing the oxide semiconductor from being damaged by the etchant used to form the source and drain electrodes. For example, see the SID International Symposium, Digest of Technical Papers May 2008, 42-2, page 625, Je-hun Lee et al.
However, in a manufacturing process of a field-effect transistor, as the number of layers of the field-effect transistor increases, the number of steps of photolithographic process increases, and many photomasks used in the steps of photolithographic process are required. Hence, if the etching stopper layer must be utilized, the field-effect transistor manufacturing process becomes complicated. To avoid this, a method for manufacturing a field-effect transistor which does not require the use of the etching stopper layer is demanded.